Abstract
A comparison of two standard humidity generators (two-temperature (2-T) and one-temperature (1-T) generators) that are developed by the National Institute for Standards (NIS) has been performed using a transfer standard chilled-mirror hygrometer and measurement procedures to realize dew-point temperature Td in the range from −50 °C to 0 °C. The main objective of this comparison was to compare the realizations of dew-point temperature and to establish the level of consistency between the two generators. For a level of consistency between two measurements, it is expressed by the difference between the measured values, m1 − m2, and the expanded pair uncertainty of this difference Up [1]. The comparison measurements revealed dew-point temperature differences of 0.02 °C and 0.07 °C with expanded pair uncertainties of ±0.09 °C and ±0.15 °C.
Highlights
There are several techniques available to generate humidity references by using stream of saturated gas with well-known water-vapor content to be used in calibration of chilled-mirror hygrometers
These techniques such a dew-point generator: generators based upon a so-called two-temperature method, generators based upon a one-temperature method and generators based upon a two-pressure method [2,3,4]
Measurements of the generators temperature were recorded at the same time of measurements of the calibrated chilled-mirror hygrometer
Summary
There are several techniques available to generate humidity references by using stream of saturated gas with well-known water-vapor content to be used in calibration of chilled-mirror hygrometers These techniques such a dew-point generator: generators based upon a so-called two-temperature method, generators based upon a one-temperature method and generators based upon a two-pressure method [2,3,4]. The main target of developing the (2-T) generator was to improve the measurement uncertainty These two generators have been developed and characterized at NIS with different saturator designs for primary realization of the dew-point temperature scale. Both of the generators are based on the saturation of a constant flow of air with respect to a plane surface of liquid water at elevated pressure.
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